1. Field of the Invention
This invention relates to a high-performance C/C (carbon/carbon fiber) composite produced by means of intercalation and to a method for the production of the C/C composite.
In view of its super-heat resistant characteristics, the C/C composite is already being used in airplane brakes and fuel cells, for example, and other promising future fields of application include aerospace (e.g. rockkets) fusion reactors, and nuclear reactors.
The C/C composite is produced by mixing carbon fibers as a reinforcing agent with pitch or resin as a precursor of a carbon matrix and firing the resultant mixture. It, therefore, comprises a carbon matrix produced by firing the precursor and carbon fibers used as a reinforcing agent.
2. Description of the Prior Art
C/C composites have attracted attention as materials with high utility in extremely high temperature applications and various efforts have been made toward improving their performance. The factors which determine whether a C/C composite can be effectively used at extremely high temperatures are the kind of carbon fibers, the kind of carbon of the composite matrix, the condition of the carbon fibers in the matrix, and the temperature at which the precursor of the matrix carbon is fired for carbonization.
It has been demonstrated that properties of the C/C composite such as mechanical strength and thermal conductivity heavily hinge not only on the kinds of raw materials and the method of production but also on the condition of the interface between the carbon fibers and the carbon matrix. With existing techniques, however, it is difficult to control the condition of this interface.
In the carbonization of a low molecular compound such as pitch, when a Lewis acid such as aluminum chloride is added to the reaction system, it functions as a catalyst for the cationic polymerization reaction and enhances the carbonization yield and ensures production of carbon of a high capacity for graphitization. On the other hand, when potassium is added to the reaction system instead of a Lewis acid, a reaction having an anion radical as an intermediate proceeds prior to the carbonization reaction. The result is a carbon that has low capability for graphitization.
It is well known that an interlayer compound can be formed between layers of graphite by intercalating a guest substance such as aluminum chloride, potassium or other such chemical species. The intercalated chemical species generates an interaction in the ionic bond between the host and the guest. When this interlayer compound is heated to between about 100.degree. C. and about 800.degree. C., the guest chemical species is liberated deintercalated from between the layers of graphite. This temperature range approximately coincides with the temperature range in which the low molecular compound begins to undergo carbonization.
The present inventors focused their attention on the interrelation between the aforementioned reaction of catalytic carbonization and the nature of the graphite interlayer compound. They consequently found that the properties of the C/C composite such as strength and thermal conductivity can be improved by using carbon fibers obtained by intercalating therein a carbonizing catalyst as a guest substance and further that the interface between the carbon fibers and the carbon matrix in the C/C composite can be easily controlled by controlling the amount of the guest substance intercalated. This invention has been accomplished on the basis of this finding.